Topological phase transition and robust pseudospin interface states induced by angular perturbation in 2D topological photonic crystals.

In recent years the research about topological photonic structures has been a very attractive topic in nanoscience from both a basic science and a technological point of view. In this work we propose a two-dimensional topological photonic structure, composed of a trivial and a topological photonic crystals, made of dumbbell-shaped dielectric rods. The topological behavior is induced by introducing an angular perturbation in the dumbbell-shaped dielectric rods. We show that this composed structure supports pseudospin interface states at the interface between the trivial and topological crystals. Our numerical results show that a bandgap is opened in the band structure by introducing the angular perturbation in the system, lifting the double degeneracy of the double Dirac cone at the [Formula: see text] point of the Brillouin zone, despite keeping the [Formula: see text] symmetry group. A pseudospin topological behavior was observed and analyzed with emphasis on the photonic bands at the [Formula: see text] point. We have also investigated the robustness of these pseudospin interface states and, according with our numerical results, we conclude that they are robust against defects, disorder and reflection. Finally, we have shown that the two edge modes present energy flux propagating in opposite directions, which is the photonic analogue of the quantum spin Hall effect.

Spectrum of the tight-binding model on Cayley trees and comparison with Bethe lattices.

There are few exactly solvable lattice models and even fewer solvable quantum lattice models. Here we address the problem of finding the spectrum of the tight-binding model (equivalently, the spectrum of the adjacency matrix) on Cayley trees. Recent approaches to the problem have relied on the similarity between the Cayley tree and the Bethe lattice. Here, we avoid to make any ansatz related to the Bethe lattice due to fundamental differences between the two lattices that persist even when taking the thermodynamic limit. Instead, we show that one can use a recursive procedure that starts from the boundary and then use the canonical basis to derive the complete spectrum of the tight-binding model on Cayley trees. Our resulting algorithm is extremely efficient, as witnessed with remarkable large trees having hundreds of shells. We also show that, in the thermodynamic limit, the density of states is dramatically different from that of the Bethe lattice.

Improving Seismic Inversion Robustness via Deformed Jackson Gaussian.

The seismic data inversion from observations contaminated by spurious measures (outliers) remains a significant challenge for the industrial and scientific communities. This difficulty is due to slow processing work to mitigate the influence of the outliers. In this work, we introduce a robust formulation to mitigate the influence of spurious measurements in the seismic inversion process. In this regard, we put forth an outlier-resistant seismic inversion methodology for model estimation based on the deformed Jackson Gaussian distribution. To demonstrate the effectiveness of our proposal, we investigated a classic geophysical data-inverse problem in three different scenarios: (i) in the first one, we analyzed the sensitivity of the seismic inversion to incorrect seismic sources; (ii) in the second one, we considered a dataset polluted by Gaussian errors with different noise intensities; and (iii) in the last one we considered a dataset contaminated by many outliers. The results reveal that the deformed Jackson Gaussian outperforms the classical approach, which is based on the standard Gaussian distribution.

Tunable terahertz absorption in Si/SiO2-graphene multilayers: disorder and magneto-optical effects.

In this work we theoretically investigate the influence of disorder and external perpendicular magnetic field on terahertz (THz) absorption in graphene/SiC cap layers on top of one-dimensional photonic structures. We show that left-handed circularly polarized light absorption can be achieved up to 0.9 and even nearly perfect absorption at magnetic fields over 4 T. It is also demonstrated that multichannel absorption can be obtained, in a broad frequency range, by increasing the disorder strength in the layer thicknesses, outperforming the corresponding periodic structures. Altogether, our results reveal the potentialities of introducing disorder to not only enhance but also to tune absorption in photonic superlattices with graphene under the influence of an external magnetic field, allowing for applications such as THz circular polarization selective sensors and photodetectors.